The Australian Transport Safety Bureau (ATSB) is Australia's national transport safety investigator. The ATSB's function is to improve safety and public confidence in the aviation, marine and rail modes of transport. The ATSB is Australia's prime agency for the independent investigation of civil aviation, rail and maritime accidents, incidents and safety deficiencies.

At 1526 Central Standard Time on 4 September 2012, a Bombardier DHC-8-202, registered VH-ZZJ (ZZJ), was cleared to takeoff on runway 29 at Darwin airport, Northern Territory. At 1528 and before ZZJ had commenced takeoff, an Aerospatiale AS.332L1, registered VH-LOJ (LOJ), called ready on runway 36. The Aerodrome Controller (ADC) cleared LOJ for takeoff and instructed the pilot to maintain upwind.

The pilot of ZZJ heard the transmission and, believing that there would have been a risk of a collision if he commenced takeoff, delayed his departure until after LOJ had crossed the intersection of the two runways. The action of the pilot of ZZJ to delay takeoff reduced the likelihood of a more serious incident.

Air traffic services at Darwin are provided by the Department of Defence (Defence). The Defence investigation found that an unsafe takeoff clearance had been issued to LOJ, resulting in a runway separation breakdown. Further, the ADC failed to monitor both ZZJ and LOJ during a critical phase of operation – takeoff. The actions of the pilot of ZZJ, by delaying takeoff, reduced the severity of the incident.

The pilot of ZZJ did not query the ADC’s instructions at the time and did not report the incident until two days later. The pilot of LOJ was not aware of the incident and the ADC did not recall the incident.